I was absent from the forum for a while due to other obligations.
Yet, this summer I managed to make a few dives with the ROV and I also managed to destroy it 2 or 3 times.
Anyway, I learned a lot through these dives about the equipment and its behavior underwater.
After our initial testing to 14-15m, (https://www.youtube.com/watch?v=KAT13i_dbgI) and after re-sealing the fuses in the battery box, I was pretty sure that all will be OK at least to 20m.
So, on our first dive at the end of July we had a blown up buoy at 17m! (See photo).
- Broken_buoy.JPG (111.43 KiB) Viewed 3211 times
The next day I made a new buoy for 10Atm which made it through the summer and reached at 21m depth without any explosions or leaks.
After that, we made another dive aiming at 20m. At 9m the U/D motor failed. After a little search, I discovered that the DPDT relays were not responding to the orders of the switch. I concluded that they had been burned since the load (approx. 5A at sea surface) was close to their capacity (8A). So, I thought, at 9m depth, the loading is higher and the relays failed.
I decided to make a new relay control and dive again. This time I followed a different wiring with 2 SPDT relays (instead of 2 DPDT mini-relays) for each motor (http://www.robmeyerproductions.com/bows.html)[/url] that were much stronger (30A) and readily available at my home town (also quite cheap 3.5Euros each).
After some days, I had prepared the new control. It worked fine until I pot it (in liquid glass). When the liquid glass cooled, I found out that the left motor wasn’t responding!. The relays though were responding (you could hear the characteristic ‘click’ when the relay switched position). I had to go for some dives anyway, and I needed the ROV for its cameras so I took it along even without one motor.
We tried it at 21m, and at this depth the bottom camera failed (something about the wiring) and the battery made a short-circuit burning the wires, and most probably the relays. All in one dive!
I was so disappointed after all these failures that I thought to cut the tether and drop the thing to Marianna Trench.
Yet, after 6 weeks, I can see things more clearly (I still don’t want to touch the ROV) and I have the courage to share the experience.
There are some positive things after all these (failed) trials:
1) The bildge pump motors (Johnson 1600 gph) worked fine after 2 dives below 15m (one at 21 and one at 19).
2) The 10Atm PVC buoy held at 21m.
3) The motors, with PC cooling fans as props (7 blade – Ø70mm) are quite strong in pushing down the ROV with a speed of approx. 18-20m/min (I have no records about the Upward speed).
I also decided to change the frame (copper pipe) because it is too big for my needs and too heavy (6.5 kg). I’m thinking of making a new one either of Polypropylene (http://www.borealisgroup.com/pdf/litera ... _10_BB.pdf) pipes (I can’t find PVC pipes of small diameter in Greece) or Aluminium.
My major problem is the sealing of the battery. I’m thinking of using an Otterbox (if I find a small enough battery that fits to an otter box then I might use one.) Has anyone really tried it to its limits (30m)?. How can I seal the holes that I’ll open for the wires?
Any other suggestions would be most welcome!
